Combined effects of inversed ratio ventilation (IRV) with positive end-expiratory pressure ventilation (PEEP) on cardiorespiratory function in acute respiratory failure.

Combined effects of inversed ratio ventilation (IRV) with positive end-expiratory pressure (PEEP) on cardiorespiratory function were examined in 24 patients with acute respiratory failure. Patients were divided into two groups: the IRV group (n = 12) who showed no significant increase in Pa(O)(2) with a 6 cmH(2)O of PEEP and PEEP group (n = 12) who were ventilated mechanically with PEEP only at maximum level of 10 cmH(2)O. In IRV group step-wise prolongation of the I : E ratio from 1 : 1.9 to 2.6 : 1 or 4 : 1 was applied as a Pa(O)(2) was improved and in PEEP group also level of PEEP was increased from 0, 5 to 10 cmH(2)O after one hour period irrespective of Pa(O)(2). Inversed ratio ventilation and PEEP increased significantly Pa(O)(2)/F i(O)(2), the increase being observed 6 hrs (I : E = 2 : 1) and 2 hrs (10 cmH(2)O) after starting IRV or PEEP. Further improvement of oxygenation was not observed in IRV even if I : E ratio was prolonged up to 2.6 : 1 or 4 : 1. These results suggested that combinations of IRV with PEEP were effective and an I : E ratio of 2 : 1 may be optimal, and IRV is advantageous compared to PEEP, but will take more long time to improve oxygenation than PEEP.